PROGRESS REPORT PROJECT 2120431 FROM BEGINNING OF PROJECT TO JUNE 30, 1964

• Document Type: CREST
• Collection: NGA Records (Formerly NIMA)
• Document Number (FOIA) /ESDN (CREST): CIA-RDP78B04747A001100040003-3
• Release Decision: RIFPUB
• Original Classification: K
• Document Page Count: 1
• Document Creation Date: December 28, 2016
• Document Release Date: April 12, 2001
• Sequence Number: 3
• Content Type: REPORT

Approved For Release 2001/07/16 : CIA-RDP78B04747A001100040003-3
Progress Report
Project 2120431
From beginning of project to June 30, 1964
This project is concerned with methods and physical standards for the
calibration of the length scales and photometric scales of microdensitometers.
Before a microdensitometer can be calibrated with respect to the length
and uniformity of travel of the stage, it is necessary to ascertain the regu-
larity with which the table moves with respect to the ways and the screw. The
various kinds of measurements which must be made have been ascertained and a
method applicable in the field has been developed for measuring these charac-
teristics. These methods have been applied by scientists in the Engineering
Metrology Section of the National Bureau of Standards to the microdensitom-
eter in use in the Photographic Research Section. By the use of a collimator
and mirror system, it was determined that the angular tilt of the table
measured in the center of travel due to direction of travel was found to be
0.4 seconds in the vertical plane and 1.6 seconds in the horizontal plane.
The spacing between the microscope mount and the working surface on the table
was found by dial indicator not to vary by more than 0.0002 inch with the
table traversed through the full range of 25 centimeters.
Resolution targets having spatial frequencies to 1,000 lines per milli-
meter have been produced. Further experiments are being done to improve the
quality of such resolution charts.
In the past, the density scales of microdensitometers have been cali-
brated by means of photographic step tablets having known densities as
defined in the American Standard for Diffuse Transmission Density. This kind
of density is inappropriate for the calibration of microdensitometers because
the geometrical conditions of illumination and sensing in such instruments
differs greatly from the geometrical conditions specified in the American
standard. Microdensitometers commonly employ high numerical-aperture illu-
mination and sensing. These high numerical apertures are necessitated by the
high resolution required of these instruments. In the American standard
method, the sample is illuminated with a pencil of light having a very small
cone angle and the light transmitted by the film is collected by an integrat-
ing sphere regardless of the angle at which it leaves the sample. A new
kind of density has been defined, having geometrical conditions of illumina-
tion and sensing identical to those employed in microdensitometry. A
"standard microdensitometer" has been constructed to calibrate photographic
step tablets for the purpose of calibrating microdensitometers. The numeri-
cal apertures of the illuminating and sensing system are variable from 0.012
to 0.65.
Declass Review by NIMA/DOD
Approved For Release 2001/07/16 : CIA-RDP78B04747A001100040003-3